Programs his company creates for U.S. colleges and universities can contain 600 to 1,200 short video clips and interviews with as many as 40 students and professors, he said.

Abi Mandelbaum, whose company, YouVisit, creates virtual walking tours for universities, said about 80 percent of applicants would visit no more than four college campuses physically. Students indicated that campus visits were a major factor in their decision making.

Students who visit schools, even virtually, “are better informed students, so if they decide to apply, they will actually be a much better fit,” he said.

George Comeau, director of interactive and digital communications at Suffolk University in Boston, said his school’s virtual tour had been viewed 151,000 times, or more than 100 times a day on average, since it began in 2008.

What he found most encouraging was that the average session time was 11 minutes and 50 seconds. “If someone is willing to spend 11 minutes with you, that’s an eternity,” he said. Virtual tours can also help increase yield numbers, or the percentage of accepted applicants who end up enrolling, Mr. Comeau said.

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With the help of CampusTours, Suffolk has developed a second tour with a more in-depth look at departments and disciplines for students who have been accepted.

Mr. Carson, the head of CampusTours, said the secret to building good tours was to reflect the feeling of the individual universities, offering “tours that break that cold institutional tone.”

Besides catering to American applicants — particularly those who are looking farther afield or cannot afford to visit distant campuses — online presentations are focusing on the growing number of international students.

According to YouVisit, 11.7 percent of visits to its sites come from abroad. Meanwhile, 25 percent of YouVisit’s campus tours are offered in multiple languages, most often in Chinese and Spanish, Mr. Mandelbaum said.

Though the trend started in the United States, virtual visits are moving to other parts of the world. This autumn, CampusTours will expand to Europe, where individual universities have been holding virtual tours for years.

Ian Bartlett, head of publications and marketing services at University College London, said its virtual tours aimed to “demystify the place for students.”

He said it was important to show the school to students who might not think of making the trip on an open day. The virtual tour, which has been online for 18 months in its current form, is a way to encourage wider access to the institution.

Jon Beard, director of undergraduate recruitment at the University of Cambridge, said by e-mail that its virtual presence could help encourage students who would otherwise “lack the confidence to make an application.”

“What we wanted to do was create a Web presence which allowed us to use a different tone to the institutional site,” Mr. Beard said.